improve quantenna detection

it seems some devices only send a 30-byte long tag containing the
vendor OUI, unlike all other chip vendors.

src/80211.c

@@ -590,8 +590,8 @@ int parse_beacon_tags(const u_char *packet, size_t len)
 			const u_char *tag = tag_data + ie_iterator;
 			// check for the length of the tag, and that its not microsoft
 			if(tag[0] == VENDOR_SPECIFIC_TAG &&
-			   tag[1] < 11 &&
 			   ie_iterator+2+3 < tag_len &&
+			   (tag[1] < 11 || (tag[1] == 30 && !(memcmp(tag+2, "\x00\x26\x86", 3)))) &&
 			   memcmp(tag+2, "\x00\x50\xf2", 3)) {
 				set_vendor(1, tag + 2);
 				break;